The present invention relates to a method of making of an electronic parts mounting board usable in electronic control equipment which may be used to control a heavy-current load such as motorcar headlight, window wiper, motor or the like.
In the past, the electronic parts mounting boards used in such electronic heavy-current load equipment have been made by forming a thickened pattern on an epoxy resin-impregnated glass cloth for printed circuits board or by applying a pattern-cut brass, copper sheet on the epoxy resin-impregnated glass cloth for printed circuits board. However, such boards could not sufficiently be satisfied in reliability, cost, occupying area and other respects.
To improve the boards with respect to these respects, it has been proposed to coat a circuit pattern on an electronic parts mounting board with an insulation resin.
FIG. 11 of the accompanying drawings is a perspective view of an electronic parts mounting board according to the prior art, on which electronic parts have been mounted while FIGS. 12A, B and C are respectively plan view, side view and front view which illustrate the electronic parts mounting board of FIG. 11 having no electronic parts mounted thereon.
Referring to FIGS. 11 and 12, the electronic parts mounting board according to the prior art comprises a circuit pattern portion 40 formed by punching a conductive sheet of metal such as brass or the like (see FIG. 12C), first and second male terminal portions 41, 42 formed by turning the opposite sides of the circuit pattern portion 40 down at right angle, a first covering portion 43 of insulation resin covering the middles of the first male terminal portions 41, a second covering portion 44 of insulation resin covering the middles of the second male terminal portion 42, and a third covering portion 45 of insulation resin covering the whole top and bottom of the circuit pattern portion 40.
The first and second male terminal portions 41, 42 are used as connectors for power lines, load devices and other electronic control devices.
The first and second covering portions 43, 44 are provided to maintain the alignment correction and terminal strength in the respective first and second male terminal portions 41, 42.
The third covering portion 45 is formed with a plurality of openings 47 for electrically connecting relay parts or electronic parts 46 to be mounted such as hybrid boards and so on to the circuit pattern portion 40, for example (see FIG. 12A).
The electronic parts mounting board of the prior art may be manufactured by the following process: First, a conductive sheet is punched out by a press die to provide a desired circuit pattern portion 40. At the same time, various electronic parts mounting through-holes, first male terminal portion 41 and second male terminal portion 42 are formed in the circuit pattern portion 40. The circuit pattern portion 40 includes bridge portions for connecting all the circuits together.
Second, the punched intermediate product is set in an insert mold. A molten insulation resin is then injected into the mold cavity to form first, second and third covering portions 43, 44 and 45 on the middles of the first and second male terminal portions 41, 44 and the opposite faces of the circuit pattern portion 40, respectively.
Third, the bridge portions connecting the circuits together in the circuit pattern portion 40 are severed, if necessary.
Finally, a bending die is used to turn the first and second male terminal portions 41, 42 down at right angle. In such a manner, the complete electronic parts mounting board is formed.
However, the electronic parts mounting board according to the prior art has the following problems.
(1) Since the turned parts of the first and second male terminal portions 41, 42 are not covered with the resin, the electronic parts mounting area is reduced. Where many electronic parts 46 are to be mounted on the board, the mounting area must be increased. This increases the board in size.
(2) Since the turned parts of the first and second male terminal portions 41, 42 are not covered with the resin, any leakage may be created due to adhesion of water or the like. In fact, the turned parts have been coated with any suitable anti-leakage material. However, such a coating was difficult. The coating material may drop onto the circuit pattern portion 40, leading to contact failure.
(3) Three covering portions require a mold having at least three gates for injecting the resin material on formation of these three covering portions. This increases the mold manufacturing cost.
(4) The first and second male terminal portions 41, 42 were bent or turned after the resin molding step. This increases the number of steps for manufacturing the electronic parts mounting board and also requires an exclusive bending die. This also increases the mold manufacturing cost.
It is therefore an object of the present invention to provide a method of making an electronic parts mounting board which can have an increased electronic parts mounting area, be reduced in size, be prevented from creating the leakage and be manufactured inexpensively.
Another object of the present invention is to provide a method of making an electronic parts mounting board which can be reduced in manufacturing steps to decrease the manufacturing cost.
The present invention provides a method of making an electronic parts mounting board, comprising the steps of:
stamping a conductive sheet to form a circuit pattern portion and through-holes in which electronic parts are to be mounted by use of a progressive die device while at the same time partially folding said circuit pattern portion to form connection terminal portions by use of said same progressive die device; and
molding an insulative resin over the whole opposite sides of said circuit pattern portion and the base ends of the terminal portions including the folded parts thereof to form an integral covering portion having openings for electrically connecting said circuit pattern portion to electronic parts to be mounted thereon.